The invention relates to centrifugal separation apparatus, and more specifically to a separator for removing hard, dense foreign objects from food products.
Separation of mixed substances of differing densities, particularly in liquids or fluidized slurries, has been carried out in many instances by the use of centrifuges. For example, see the disclosures of U.S. Pat. Nos. 3,880,347, 2,741,333 and 2,782,925. The first listed patent shows a light and heavy material centrifuge separator in which the heavies were passed through an outer port while the lights were passed through an inner port. The fluid mixture entering the centrifuge inlet had to be pressurized in order to move the separated components, particularly the heavies, through the apparatus to the outlet. A portion of the travel was against centrifugal force.
U.S. Pat. No. 2,741,333 cited above, shows a centrifuge for separating impurities in oil, with a peripheral annular space divided into separate dirt pockets. This separator also required the entrance of the input fluid under pressure.
U.S. Pat. No. 3,702,704 disclosed a noncontacting seal for a centrifuge. However, the seal was concerned with preventing slurry leakage at the entrance to a centrifuge rather than downstream, where a different type problem arises with the centrifuge-pumping apparatus of the present invention described below. Moreover, the structure of the disclosed noncontacting seal is quite different from that of a noncontacting seal included in the present separator.
In the food industry there has been an acute need for a device which will efficiently remove hard foreign matter, particularly bone, glass, plastic, and metal fragments, from a food product without changing the physical character (e.g., the chunk size and shape) of the product. This has been true particularly in recent years, wherein automated processes have been increasing, adding to the risk of contamination by these substances. Bolts, metal shavings, etc. from equipment often find their way into food products. Buckshot, fence nails, barb wire, etc. are often present in beef. Dectectors for metals, in particular, have been plentiful although very costly. The detectors, however, do not actually remove the impurities, and large quantities of contaminated product must simply be dumped for lack of a way to separate the product from the contaminants. There have been magnetic separators useable with very fluid products, but these have been unable to remove anything but ferrous metal impurities.
Hughes U.S. Pat. No. 4,015,784 is directed to a food batter emulsifying apparatus involving a centrifuge disposed upstream of a series of emulsifying orifices. The centrifuge has been found effective to remove heavy impurities such as metal fragments from the input slurry. However, the disclosed apparatus has not been found useful for the purposes for which the present invention is intended, for several reasons. For one thing, the metal impurities caught are not truly trapped, but are allowed to fall into emulsifying orifices directly below the peripheral wall of the centrifuge chamber whenever the rotation of the machine is stopped, posing a risk of recontamination. Even if the foreign matter were contained in the centrifuge, it would be difficult to retrieve, since there is no easy way of uncovering the centrifuge chamber for cleaning. A very important difference between the Hughes machine and the present invention is that food material cannot go through Hughes' centrifuge without being changed in character, i.e. broken up and crushed. An initial part of the emulsifying is actually performed in the centrifuge chamber, where an impeller strikes the product and there are obstructions against which product chunks are beaten and caught. The fact is that Hughes' device is effective for its intended purpose as an emulsifier, but cannot serve the purposes of the present invention due to very important structural differences.
No centrifugal separating device of the prior art has been capable of performing the dual functions of efficient foreign matter separation, without separation of lights and heavies of the product itself, and handling of the product in such a way as to avoid tearing, crushing, emulsifying and other damage to the prouduct's components.